Apparatus is shown providing flame-less heat, particularly converting mechanical shaft power to flame-less heat, and specifically converting mechanized shaft power into electrical heat.
There are situations, such as on oil fields, where traditional methods of generating heat are not accepted. Unacceptable forms of heat generation include “flame-type” devices that burn a variety of fuels such as natural gas, fuel oil, propane, diesel fuel, etc. Use of diesel engines is commonly accepted for use in these “no flame” zones. It is common for heat to be generated using diesel engines in a portable system to provide either hot air or hot water in these special zones. Naturally, a system of this type would scavenge heat from the engine coolant and perhaps the exhaust stream and/or the turbo-charger. To make a system like this work, there must be some manner of applying load to the engine shaft to create the waste heat that may be reclaimed. Various ways have been devised to convert the mechanical shaft power to heat so that the air or water is heated by the sum of the scavenged heat and the conversion of mechanical power to heat. Specifically, conventional devices utilize various forms of fluid shear or magnetic fields to create heat in metals or directly in fluid.
Such devices are typically run by taking in 100% outside air, which is quite often in sub-zero temperatures. Diesel engines typically have about 35% of the energy of the fuel discharged through the exhaust stack. Given that these systems can consume large quantities of fuel per day, thermal efficiency is important. Common practice for engine heat reclaim in these portable systems is to have the coldest outside air pass through the cooling radiator first before reclaiming heat from the exhaust. The radiator is typically in front of the engine, which is near the front of the trailer where intakes are located. Sometimes, different heat exchangers are employed to reclaim some energy from the exhaust, but in one way or the other, they all reclaim heat using air that has been already heated by engine coolant reclaim. Some route hot fluid from the mechanical heat conversion process through a liquid-to-air exhaust heat exchanger, and others simply route extra lengths of exhaust piping in the air plenum where this pre-heated air passes.
Fluid devices have a number of serious limitations. The fluids are prone to leak, because there are rotating mechanical elements with seals, pumps with seals, and control valves that can also leak. The durability of the seals is weakened by the fact that the fluid temperature is high. Since discharge temperatures of the air are desired to be above 200° F., the fluids will operate above 250° F. and, under some process interruptions, can rise much higher. Another limitation is foaming and breakdown of the fluid. Foaming causes sensors to be misread and interrupts the steady flow to transport heat away from the converting device. Yet another limitation is cavitation that erodes the shear device surfaces resulting in lack of reliability and the cause of much maintenance expense. The limited operating life typically requires that complete overhauls be performed after a few months of use.
The methods used to control the amount of engine load are themselves a maintenance issue and result in reduced reliability. Conventional systems also require that the engine be run at full speed regardless of load, thus adding more wear to the engine.
Thus, a need exists in the field of providing flame-less heat for methods and apparatus which are efficient, reliable and requiring less maintenance.